I've played quite a bit with IJA. I usually run an infantry battalion as my core force. Depending on the type of mission, I'll get to spend support points on Armor, Engineers and Recce if it's an Assault or AT guns if its a Defend.

It used to be far easier for the infantry to be successful in their close assaults on armor. And the standard IJA infantry has sufficient Morale to attempt close assaults.

The LC for Japan from 1937 will take you across at least 2 years of fighting Nat Chinese and Chinese Communists, before going against Soviets from '38 to '39. That's a pretty good time to fight against the Soviets, they do not have such heavy armor yet.

Then if you continue till '41, you'll have the opportunity to go into SouthEast Asia against British forces. By '42-'43, you'll be able to fight against USA, UK, Australia till end of the war. It's a very wide-ranging LC.

I've had my battalion rebuilt several times. Their equipment never did improve as the war got on, so it always got comparatively more challenging.

I've had to put my IJA campaign on hold for the time being since I'm trying out Monty's DAS REICH mod for Steel Panthers MBT. I actually started mine in 1931 in Manchuria and found it a very refreshing change of pace. It is very infantry focused as you said, and I think it might take some getting used to to not see periodic upgrades for my infantry I did enjoy exploring a new order of battle and approaching the game from a fresh perspective, and I fully intend to return to Imperial Japan at some point to get my fill of infantry combat in the jungles of the pacific and asia.

But you're absolutely right, it does get very challenging as things go on. Primarily I think because of the artillery situation and less because of the armor: the Japanese infantry can handle most tanks if they use the terrain correctly, but the Allied infantry can be rough to deal with since Japanese infantry battalions have less or lower quality artillery than a lot of their European counterparts. In the battles I played I felt like I was relying much more on my machineguns and my snipers to fix the enemy so that I could overwhelm them with fire. Tanks (I only bought one company and broke it up amongst the battalion of infantry) were also useful for this but so painfully slow and undergunned that you couldn't expect them to handle everything on their own.

So this gives me integral artillery, infantry, engineering assets, armor and tons of recon. I also have a Kradschutzen company tagging along that I'll drop for an under-strength Tiger company later in 1943. Overall this is more of a "Kampfgruppe" than an on paper infantry battalion. Its very flexible and probably heavy on the artillery, but considering how much arty I have to receive from the Allies and Soviets I stopped feeling bad about that really quick. Its often essential for breaking massed infantry attacks.